DECLARATIONS OF INTEREST 589

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The authors declare that they have no known competing financial interests or personal 590

relationships that could have influenced the work reported in this paper.

591

592

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SUPPLEMENTARY 765

Table S1. The chemical parameters of the water-matrices 766

Parameter River water

(River Tisza, Hungary)

Biologically treated domestic wastewater

pH 7.2 7.8

Conductivitiy (µS cm⁻¹) 671 1258

COD (mg dm⁻³) 12.8 24.4

NH4

+−N (mg dm⁻³) < 0.4 < 0.4

NO3−

(mg dm⁻³) 7.84 3.37

Cl⁻(mg dm⁻³) no data 120

TOC(mg dm⁻³) 3.8 6.9

HCO3−

(mg dm⁻³) 148 525

767

768

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Fig. S1 High resolution X-ray photoelectron spectroscopy (XPS) spectra of elements (Bi 4f;

791

O 1s; I 3d and Cl 2p) of BiOI, BiOCl and 80:20 BiOI:BiOCl composite 792

793

208 206 204 202 200 198 196 194 192 190

Intensity (a.u.)

174 172 170 168 166 164 162 160 158 156

Intensity (a.u.)

174 172 170 168 166 164 162 160 158 156

Intensity (a.u.)

174 172 170 168 166 164 162 160 158 156

Intensity (a.u.)

540 538 536 534 532 530 528 526 524 522 520

Intensity (a.u.)

540 538 536 534 532 530 528 526 524 522 520

Intensity (a.u.)

540 538 536 534 532 530 528 526 524 522 520

Intensity (a.u.)

635 630 625 620 615 610

Intensity (a.u.)

208 206 204 202 200 198 196 194 192 190

Intensity (a.u.)

635 630 625 620 615 610

Intensity (a.u.)

208 206 204 202 200 198 196 194 192 190

Intensity (a.u.)

635 630 625 620 615 610

Intensity (a.u.)

BiOCl BiOI 80:20 BiOI:BiOCl

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37 Evaluation of XPS results:

794

The peaks with the binding energies of 158.8 and 167.7 eV are attributed to Bi 4f7/2 and Bi 795

4f5/2, respectively, and represent the typical Bi³⁺. A reduced/metallic component is caused by 796

the X-ray source during the measurement and can be observed only in the case of BiOCl.

797

Lower binding energy oxygen peak component (O1s) refers to the lattice oxygen in the 798

(BiO)₂²⁺, higher binding energy peak is attributed to the surface hydroxyl groups (Liu and 799

Wang, 2016). For BiOCl only the lattice oxygen was observed, while for BiOI and composite 800

both peaks appear. The peak of Cl 2p3/2 at 197.9 eV (197.6 eV in the composite) corresponds 801

to Cl^–(Hao et al., 2017). The anomalous background of the Cl 2p spectra is due to the 802

neighboring Bi 4f peaks. The peaks of I 3d can be found at 630.0 and 618.8 eV, and attributed 803

to I 3d_3/2 and I 3d_5/2, respectively, corresponding to I^– in the BiOI (Di et al., 2016).

804

805

806 807

Fig S2 The The spectra of the LED light sources 808

809 810

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38 811

Fig. S3 The effect of the 80:20 BiOI:BiOCl catalyst dosage on the relative adsorbed amount 812

(%) and initial transformation rate of methyl orange (2.0×10^–4 M) 813

814

815

Fig. S4 The concentration of methyl orange as a function of time with and without the 816

addition of fluoride ions (80:20 BiOI:BiOCl, UV-LED) 817

818

 ads. MO (%)

r

0 SMP

 r

0 MO

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39 819

Fig. S5 The relative concentration of MO and SMP, and their primary products versus time of 820

treatment (a: MO+BiOCl; b: MO+80:20 BiOI:BiOCl composite; c: MO+BiOI, d:

821

SMP+BiOCl; e: SMP+80:20 BiOI:BiOCl composite; f: SMP+BiOI) using various light 822

sources 823

824

0 30 60 90

t (min)

0 30 60 90

0.0 0.2 0.4 0.6 0.8 1.0

t (min) c/c0

0 30 60 90

t (min)

0 200 400 600 800 1000

Area (230 nm)

0 200 400 600 800 1000 1200

Area (464 nm)

0.2 0.4 0.6 0.8 1.0

UV Cool white Warm white UV (Product) Cool white (Product ) Warm white (Product)

c/c0 SMPc/c0 MO

BiOCl 80:20 BiOCl/BiOl BiOl

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40 825

826

Fig. S6 The spectra of the treated solutions using 80:20 BiOI/BIOCl composite (a) and P25 827

photocatalysts (b), and the chemical structure of the products determined by HPLC-MS 828

BiOI:BiOCl/Vis; TiO₂/UV

SMP

41 830

Fig. S7 The XRD patterns of the 80:20 BiI:BiOCl catalyst before and after the three cycle 831

832

833

Fig S8 Effect of pH and matrix components on the iodide ion leaching from the 80:20 834

BIOI:BiOCl photocatalyst. The UV spectrum of the suspensions after stirring for 30 minutes 835

in dark 836

0.0 0.4 0.8 1.2 1.6 2.0

200 300 400 500 600

Absorbance (A.U.)

Wavelength (nm)

Ref.; pH = 6.5 NaCl NaHCO3 Na-humate NaOH; pH = 9.2 H2SO4; pH = 4.0

0.0 0.4 0.8 1.2 1.6 2.0

200 225 250 275 300

Absorbance (A.U.)

Wavelength (nm)

Ref.; pH = 6.5 NaCl NaHCO3 Na-humate NaOH; pH = 9.2 H2SO4; pH = 4.0

Iodide ion

a b

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Declaration of interests

☒The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

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